There is known an arrangement for supporting stator end windings of an electric machine (cf. Swiss Pat. No. 413,073), comprising an inner ring mounted coaxially with the bore of the stator core and supporting stator end windings, and an outer ring externally embracing stator end windings, both rings being made of electrically insulating material. In said arrangement the inner and outer supporting rings are interconnected by means of the end windings and fastening members attaching them to the end windings. Therewith the outer ring may be axially displaced relative to the stator core and is tightly connected with a stator frame in a radial direction.
Among the disadvantages of this arrangement is the relatively large number of fastening members having a comparatively complex configuration which requires an increased precision of manufacturing tolerances and complicates the assembling and adjustment of the electric machine stator winding.
Another disadvantage of this arrangement is an insufficient decrease in the level of the end winding vibrations which appear under the influence of variable electrodynamic loads during operation of an electric machine and which may result in the failure of solderings of winding bar connections, in wear and crumpling of insulation at the points of attachment and at the outlet of bars from the core slots, and in fatigue damage to elementary copper conductors of winding bars. This disadvantage results for the following reasons. Firstly, the inner and outer supporting rings are mounted at a relatively large distance from the end winding heads wherein, during operation of an electric machine, the end windings, as a rule, have a maximum level of vibrations. Secondly, the inner ring has a small cross sectional area compared to the cross-sectional area of the end windings and, consequently, it cannot increase the total rigidity of the entire end winding supporting arrangement as required. However, it is common knowledge that a high rigidity of a supporting arrangement is one of the main factors in reducing the end winding vibration level. Thirdly, the inclusion of a number of intermediate fastening members for securing the inner and outer rings to the end winding bars also decreases the rigidity of connection of these rings with the end windings and, accordingly, fails to provide a reduced level of vibrations.
Among the other disadvantages of the known construction for supporting end windings is the fact that the outer ring, on the one hand, is tightly connected in a radial direction with the stator frame by means of fastening members and, on the other hand, is rigidly connected with the stator winding. As a result, during operation of an electric machine end winding vibrations are superimposed by stator frame vibrations, which may cause additional variable bending strains of the winding bars in the zone where these bars pass from a slot winding portion to an end portion and that will adversely affect the strength of the bars and decrease the end widing support reliability.
Thus, the known arrangement for supporting stator end windings of an electric machine fails to provide sufficiently reliable support of end windings and, hence, does not eliminate the danger of the end winding resonance of a forcing vibration frequency which may occur during operation of an electric machine.